The present invention relates to a method of curing and crosslinking photosensitive polyimides and, more particularly, to the use of such method for photolithographically patterning layers of the photosensitive polyimides and electroplating conductor seed patterns.
Photosensitive polyimides are known dielectrics having a broad range of applications in the manufacture of integrated circuits as passivation coatings, interlayered dielectrics, alpha-particle barriers, and as insulating layers in a variety of other applications. Because of the potential of reducing the number of processing steps, there has been a drive toward photoimagable polyimide systems. The development of polyimide systems that can be applied and patterned, similar to a photoresist, and remain a permanent part of the device has been a great advantage. Although improved photoimagable polyimide systems have been developed, many of these systems currently suffer from the drawback that in order to render the polyimide completely solvent insoluble, the polyimide must be heated to a temperature in excess of about 350.degree. C.
When the polyimide layers are heated to these elevated temperatures, the associated microelectronic structures are also exposed to the elevated temperatures. This may cause several problems. For instance, chemical interaction between adjacent materials such as conductor seed lines, conductive interconnect films, or the polyimide layers can occur. Further, the elevated temperatures can cause heat-induced interdiffusion between adjacent metal layers, particularly, the delicate metal layers of the conductor seed lines. Also, the elevated temperatures can have an adverse affect on conductive films that are used as disconnect materials, particularly, those conductive films that change their conductive properties at temperatures well below the 350.degree. C. temperature required to thermally crosslink and cure the polyimides and render them resistant to solvent attack.
Therefore, the need exists for a method of effectively crosslinking and curing the photosensitive polyimides in a manner that does not cause chemical interaction, heat-induced interdiffusion or other damage to the microelectronic structures associated with the polyimides.